1. Field of the Invention
The present invention relates to mixtures of oligomers of alkylalkoxysilanes condensed in the chain and/or cyclic form, to a process for their preparation and their use.
2. Description of the Background
Alkyltrialkoxysilanes release alcohol on hydrolysis. Quantitatively, the alcohol, which is formed as a product of hydrolysis is, for example, in the case of octyltriethoxysilane, around 50% by weight of the trialkoxysilane used. Because of this fact, many potential applications for the alkyltrialkoxysilanes remain closed or are adversely affected, e.g. because of the explosion-proofing precautions required or for ecological reasons, with the keyword. The keyword here then is VOC=volatile organic compounds. However, from the applications viewpoint, in many cases it would be desirable to have substances available which have properties similar to those of the pure alkyltrialkoxysilanes, without having to accept the above disadvantages. Substances of this type could be used, in particular, in rendering mineral surfaces hydrophobic.
European Patent Application No. 0 518 057 discloses mixtures of siloxane oligomers having a degree of oligomerization of 0 to 8, with the siloxanes containing per Si atom at most one vinyl group and methoxy or ethoxy groups, with or without alkyl groups having 1 to 18 carbon atoms. In addition, 0 518 057 Al discloses a process for preparing these siloxane mixtures. The siloxane mixtures, which are distinguished because they have vinyl functional groups, are suitable, in particular, as crosslinking agents in the preparation of cable covering compounds based on thermoplastic polyolefins and for similar applications in association with crosslinkable organic substances.